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Background: A variety of public, governmental initiatives inform citizens about what is considered ‘healthy’, ‘climate friendly’, and in general ‘sustainable’ food. The ambition is to influence individual food choices. However, research suggests that, rather than public authorities, people are more likely to affect each other’s behaviour through social influence. The degree of influence though seems to depend on how people are connected and how similar they are to each other. To better understand the various dynamics occurring within social networks, researchers have experimented with controlled networks, manipulating factors like the number or kinds of ties. This increases the chances of identifying causality, yet also affects the external validity of the results since the design is very artificial. The present study tries to reduce artificiality by studying real-life behaviour and behaviour change, while including controlled treatments. The aim is to compare if and how behavioural change spreads more in groups exposed to different social network conditions and different source-types of information about food.

Method: The paper outlines a study protocol from a 4-month randomized controlled trial conducted with a random selection of adults living in Sweden from mid-October 2022 to early-February 2023. The trial was registered and reviewed by the Swedish Ethical Review Authority under ref. no. 2022-02646-01 (June 9, 2022). Using a mobile phone application, the study investigates if and how real-life, self-reported intakes of plant- and animal-based foods diffuse under certain social network conditions. The trial included two treatment groups and one control group exposed to (1) different social network conditions (with or without informational exposure), and (2) to different source-types of information about food (factual versus social).

Discussion: By investigating the roles of both social diffusion processes and certain structural conditions provided by public actors for sustainable consumption, the results contribute to discussions of how and by whom effective and efficient measures could be implemented to transform food habits.